The design and fabrication of a micro-thermal/pressure-sensor for medical electro-skin application

Abstract

In this paper, a prototype contact-type micro-thermal/pressure-sensor (MTPS) that can be utilized to measure the temperature and pressure on the micro-electro-mechanical system interface to the human burn skin was designed, fabricated and tested. The finite element method package ANSYS has also been employed for the MTPS design specification. The sensor contains two X-ducers that will transform the pressure and thermal stress into output voltages. In the developed sensor, a 2400×2400×100 μm 3 square membrane is formed by bulk micro-machining of an n-type (1 0 0) monolithic silicon. The piezoresistive strain gauges were implanted with boron ions with a dose of 10 15 atoms/cm 3. We eventually aim to analyze the hydration status and ionic environment of the outermost layer of the skin. For the thermal stress, the resistance of the developed sensor is typically 502 Ω with a nominal temperature coefficient of resistance of 0.086%/°C, which is suitable for constant current source at 3-V voltage supplied on X-ducer connections. The sensor also shows its linear relation in the real application pressure range (200–600 kPa). Thus, the developed MTPS, which has smaller weight and volume as compared to a conventional one, perform well and fit our design specifications.